The present invention relates to ion beam devices and, more particularly, to a field ionization source that is specially configured to minimize contamination of an ion beam target.
Liquid metal ion guns are used routinely to generate focused ion beams for analysis of a substrate. Liquid metal ion sources are typically very bright and are well-suited for applications requiring sharp focus of the ion beam and maintenance of a suitable ion fluence. Typically, the ion fluence of a liquid metal ion gun is of the same order as that of a field emission source of a conventional scanning electron microscope. However, liquid metal ion guns typically use gallium, indium, or gold.
The present invention embodies the recognition that gallium, indium, gold, and other conventional materials are not well suited for all ion source applications. For example, where an ion beam is to be used to analyze a semiconductor target, the use of gallium, indium, or gold as a sputter ion source material may lead to unacceptable contamination of the substrate. Accordingly, there is a need for a field ionization source that does not embody the disadvantages of the conventional types of ion sources, particularly in the context of focused ion beam defect analysis systems.